Wood burning hot air furnace



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United States Patent WOOD BURNING HOT AIR FURNACE Wayne L. Critten, Gallatin, Mo.

Application December 17, 1953, Serial No. 398,765

1 Claim. (Cl. 126-104) This invention relates to furnaces for heating one or more rooms of a building and more particularly to a novel furnace adapted for burning wood and the like.

While long ago wood was extensively used for heating of homes and the like, the burning apparatus had to be frequently recharged with wood and it was very diflicult to maintain any uniformity of heat. Therefore, wood burners have usually been supplanted with devices using other fuel such as gas, oil, coal and the like even though in some areas there are large supplies of firewood easily and economically obtainable.

The objects of the present invention are to provide a heating furnace structure for controlled burning of wood and long burning of each charge of fuel; toprovide a wood burning apparatus with automatic controls for maintaining substantially uniform temperature in the area being heated; to provide such a furnace with a horizontally arranged, elongated, cylindrical fire chamber that handles long pieces of firewood and continuously feeds the pieces downwardly to the bottom of said chamber to maintain the burning wood pieces in a closely positioned mass; and to provide such a wood burning furnace that is economical to manufacture, easily controlled and efiicient in operation in burning elongated pieces of firewood.

In accomplishing these and other objects of the present invention I have provided improved details of structure, the preferred form of which is illustrated in the accompanying drawings, wherein:

Fig. 1 is a perspective view of a furnace embodying the features of the present invention, portions being broken away to illustrate the arrangement of the fire chamber in the casing.

Fig. 2 is a vertical sectional view through the furnace.

Referring more in detail to the drawings:

1 designates a furnace which generally includes a fire chamber shell 2 having connection with a flue pipe 3, a grate 4, a casing or jacket 5 surrounding the fire chamber 2, an ashpit 6 and air ducts 7 for entry of air into the jacket and a duct 8 for movement of heated air from the jacket. The jacket 5 has a front wall 9, side walls 10 and 11, top wall 12, bottom wall 13 and rear wall 14, all suitably secured together to form a structure in which the sides, top, bottom and rear walls are spaced from the walls defining the fire chamber shell 2 which is enclosed in the jacket 5. While the jacket is illustrated as being generally rectangular in cross section, it may be round or other suitable shape that will permit air flow between the jacket walls and the fire chamber.

The fire chamber shell 2 is of elongate form, arranged horizontally and substantially centrally of the jacket 5, said fire chamber preferably being cylindrical or otherwise shaped in cross section whereby the side wall 15 slopes or curves downwardly and inwardly sufiiciently to cause any fuel in the fire chamber to gravitate toward the center of the bottom portion of said fire chamber. The forward end 16 of the fire chamber structure is suitably secured to the front wall 9 by fastening devices 17.

Patented Got. 22, 1957 The front wall 9 is provided with a frame 18 defining an opening 19 to provide access to the interior of the fire chamber, the opening being of suitable size for inserting pieces of wood in charging the chamber with fuel. The opening 19 is closed by a door 20 hingedly mounted on the frame 18 as at 21. The fire chamber shell 2 is relatively long as illustrated in Fig. 2 to receive long pieces of firewood and the closed rear end 22 of said chamber is spaced from the rear wall 14 of the jacket sufficiently for passage of air therebetween.

The flue pipe 3 is suitably connected to the fire chamber preferably adjacent the upper portion 23 of the rear wall 22, said flue pipe extending through an aperture 24 in the rear wall 14 and connected with a suitable chimney or the like (not shown). A damper 25 is pivotally mounted in the flue pipe 3 and is operable to aid in controlling the combustion of the fuel in the fire chamber as later described. A pipe 26 is arranged inside the fire chamber to form a water coil in order to provide hot water while the furnace is in operation. The ends 27 and 28 of the pipe extend through the front wall 9 and are adapted to be connected to water supply and hot water piping in the house respectively.

The grate 4 is preferably arranged in the bottom portion of the fire chamber adjacent the forward end thereof, said grate resting on a frame 29 suitably secured to the wall of the fire chamber and defining an opening 30 for ashes to pass down onto the grate. The grate is movable on the frame 29 for shaking ashes therethrough, the movement of the grate being accomplished by a shaker arm 31 suitably connected to the grate and extending through a slot 32 in the front wall 9. The ashpit 6 is under the grate 4 and is defined by the front wall 9, a bottom wall 33, a rear wall 34 and side walls 35. The side walls 35 extend downwardly from the bottom portion of the fire chamber and are fastened to the bottom 13 of the jacket. Downward extensions 35 of the jacket side walls 10 and 11 form the lower side walls of said ashpit extending below the bottom 13, whereby the bottom 33 of the ashpit is below the bottom 13 of the jacket. The rear wall 34 and side walls 35 of the ashpit are suitably connected to. the bottom wall 13 and extends upwardly therefrom and are connected as at 36 to the wall of the fire chamber shell 2, whereby the ashpit 6 is separated from the air space between the jacket 5 and the fire chamber shell 2. Legs 37 are arranged on the jacket and extend downwardly therefrom to support the furnace on a floor or other suitable base.

In the form of invention illustrated there are a plurality of ducts 7 connected to the bottom wall 13 for movement of air from various areas to be heated into the jacket for passage around the fire chamber and the heated air will then move through the duct 8 to the area to be heated. While only one duct 8 is shown, it is believed obvious that a plurality of separate ducts may be provided for separate movement of air to various areas to be heated. The ashpit is provided with a door 38 which normally closes an opening in a wall defining the ashpit whereby opening the door will provide access to the ashpit for removal of ashes therefrom. A draft door 39 is arranged above the ashpit door and controls an opening in the ashpit wall below the grate 4 whereby opening of the draft door provides for entry of air below the grate 4 for passage therethrough into the fire chamber to support combustion of the fuel therein.

It is preferable that the damper 25 and draft door 39 be automatically controlled according to the heat required in the area to be heated. Cables 40 and 41 are connected respectively to the damper 25 and draft door 39 with the other ends of said cable wound on a pulley 42 operated by a motor 43 which is reversible and connected to a suitable source of electrical current for energizing same. The motor 43 is controlled by an electric circuit including a thermostat 44 and overheat control 45 which are positioned in an area to be heated and on the top wall 12 of the jacket fi respectively, the thermo stat and overheat control being arranged whereby when the temperature of the top wall 12 of the jaclret reaches a predetermined upper limit the overheatcontrol' 45 will cause the circuit to the motor 43 to be completed for operation of same to close both the draft door 39 and damper 25. When the area to be heated has a'tempera ture below a predetermined minimum the thermostat 44 will cause energization of the motor 43 to open the draft door 39 and damper 25, and when the temperature in the area to be heated reaches apredetermined upper limit the thermostat will'operate to eftectreversal of the motor 43 to close the draft 39 anddarnper 25.

In operating a furnace constructed and assembled as described, the thermostat 44, the overheat control 45 and motor 43 are energized and a fire is started in the fire chamber shell 2. After'the fire is burning, long sticks of firewood are placed in the fire chamber through the door opening 19 to substantially fill the interior of said fire chamber, then the door 20 isclosed and the thermostat 44 controls the draft door and damper to eifect suitable burning of the firewood. The relative positioning of the grate and flue connection at opposite ends of the fire chamber and the control of the draft provide a slow burning of the firewood whereby a suitable charge of firewood in the fire chamber will provide heat for a number of hours. The contour of the bottom of the fire chamher is such that the. firewood always gravitates together for substantially uniform burning thereof.

It is believed obvious that I have provided a novel wood burning furnace that is economical to manufacture and arranged to provide uniform heat from relatively long pieces of firewood.

What I claim and desire to secure by Letters Patent is:

In a heating furnace for burning relatively long sticks of firewood, a shell forming an elongated cylindrical fire chamber closed at its rear end and arranged horizontally whereby sticks of firewood therein gravitate down the cylindrical wall toward a longitudinal central line-at the bottom of the fire chamber, a casing having side, top,,bottorn and rear walls surrounding the fire chamber and spaced from the walls thereof to provide passageways around the fire chamber, said casing having openings in the rearward portion of the bottom wall and forward portion of the top wall thereof establishing communication between the space around the fire chamber and atmosphere whereby said openings allow air to pass into said space from adjacent the rearward portion of the bottom of the casing through thespace around the fire chamher and out adjacent the forward portion of the top of the casing, a flue connection extending through the casing and having communication with the interior of the fire chamber adjacent rear end thereof, said casing having in front; wall,,. aportion of which closes the front end of the fire chamber, said front wall portion having a door for introducing firewood therein, a grate in the lower portion of the fire chamber adjacent said other end, depending side and rear walls in the casing connecting said fire chamber around the grate and the casing bottom wall, extensions on. the front and side walls of the casing and rear depending wall extending below the bottom wall of the casing, a second bottom wall connecting the lower portions of said wall extensions and cooperating therewith and said depending side. and rear walls to define an ashpit under said. grate, means forming an adjustable air inlet in the casing establishing communication between the ashpit and the atmosphere for the entry of air and passage thereof through the grate to support combustion of firewood in the fire chamber, and a damper in the line connection, said adjustable air inlet and damper being operable to regulate the combustion of the firewood in the lite chamber.

References Cited-in the file of this patent UNITED STATES PATENTS 19,683 Ehilds Mar. 23, 1858 70,679 Arthur's Nov. 12, 1867 261,035 Plummer July 11, 1882 472,183 Thedens Apr. 5, 1892 689,078 Hartford Dec. 17, 1901 852,056 Fisk Apr. 30, 1907 1,164,841 Miller Dec. 21, 1915 1,816,027 Schultz July 28, 1931 1,848,653 Persons Mar. 8, 1932 1,924,985 F'eipel Aug. 29, 1933 

